1. Field of the Invention
This invention relates to impulse jet printing. Generally, the impulse jet head structure includes an ink cavity which is periodically constricted by the application of an electrical pulse to an electromechanical element, such as a piezoelectric transducer, which is positioned adjacent to the cavity. The constriction of the cavity causes drops to be ejected from an orifice in the head structure.
The resoluton of an impulse head structure, i.e., the degree to which the size of the drops which are formed and the spacing between adjacent channels in an array structure can be controlled, is a function of the accuracy with which the orifice portion of the head structure can be manufactured. In order to provide a head structure which will meet the resolution requirements of word processing printing, tolerances on the order of 0.001 inches and better are required. These high resolution requirements have heretofore been difficult to achieve and have limited the use of impulse jet printers in word processing systems.
2. Description of the Prior Art
Generally, impulse jet head structures are made of plastic or ceramic, such as is shown in U.S. Pat. No. 4,057,807, or of glass, such as is shown in U.S. Pat. No. 3,972,474. The use of such materials limits the resolution capability of the head structure. This limited resolution capability in the manufacturing process in turn limits the accuracy in the size of drops which are ejected from the head structure, as well as how close adjacent channels in an array structure may be placed.
It is possible to etch extremely well defined grooves and holes in silicon using an anisotropic etchant which attacks different atomic planes in silicon at different rates. This etchant, which contains ethelyene diamine, pyrocatechol and water, is widely used in the semiconductor industry in the fabrication of integrated circuit devices. Because of the ability to produce very high resolution grooves and holes in silicon wafers, the anisotropic etching technique has found application in other areas, such as the manufacture of strain gauges and micro-optical fixtures to align fiber optics with other optical components. Other applications more closely related to the present invention have also been developed. Ink jet nozzles made from a silicon substrate are disclosed in U.S. Pat. Nos. 3,921,916 to Bassous, 3,958,255 to Chiou et al., and 4,007,464 to Bassous et al. U.S. Pat. No. 4,047,184 to Bassous, et al. discloses a combined nozzle and charge electrode structure which is formed by etching a silicon substrate. The use of etched silicon substrates in ink jet printers has been limited, however, to individual components, such as the nozzle or charge electrode, and has not been applied to the formation of an entire impulse jet head structure.